1. Field of the Invention
The present invention relates generally to rear door systems for transferring hot cell equipment, and, more particularly, to a rear door system for transferring hot cell equipment which has an improved structure such that a vertical moving table is vertically moved on the rear door of a large hot cell that handles highly radioactive material but cannot have a roof door, so that an operation of transferring the hot cell equipment, which is relatively large or heavy and is highly radioactive, into or out of the hot cell can be conducted using only the rear door, thus making it easy to transfer the hot cell equipment, and preventing a user from being directly exposed to radiation, thereby preventing the user from being subjected to safety hazards that may occur when transferring the hot cell equipment.
2. Description of the Related Art
As well known to those skilled in the art, large hot cells, which handle highly radioactive material, include rear doors and roof doors.
Here, in the case of hot cell equipment which is relatively small and light and has relatively low radioactivity, the rear door is opened, and then the hot cell equipment is carried into or out of the hot cell therethrough. In the case of hot cell equipment which is relatively large and heavy and has relatively high radioactivity, the roof door is opened and, thereafter, the hot cell equipment is carried into or out of the hot cell therethrough using a crane, which is provided in a service area.
Meanwhile, of the hot cells that handle highly radioactive material, in the case of a hot cell which has no roof door, the hot cell equipment, which is relatively large and heavy and has relatively high radioactivity, cannot be carried into the hot cell. Thus, in the case where there is no roof door, only hot cells that handle radiation material that is relatively small and have relatively low radioactivity have been constructed.
As such, of the hot cells that handle highly radioactive material, in the case of a hot cell which is provided with a rear door but has no roof door, all of the hot cell equipment is carried into or out of the hot cell through the rear door.
Here, in the case of the large hot cell which handles highly radioactive material, radiation shielding walls constituting the hot cell are very thick. Therefore, in space defined by the rear door and areas adjacent to the corresponding radiation shielding wall, there are some areas that a crane in the hot cell and a crane in the service area cannot approach. Hence, there is a problem in that it is difficult to carry the hot cell, which is heavy or large, into or out of the hot cell.
Furthermore, typically, the height of a hot cell working table, which is installed in the hot cell, is 900 mm, and the height of an opening defined by the rear door is 2000 mm. Therefore, the height of a space between the upper end of the opening, defined by the rear door, and the hot cell working table is 1100 mm. However, taking the curved edge of the working table into account, the effective space between the upper end of the opening and the working table is less than 1100 mm. Therefore, it also is very difficult to carry the hot cell equipment, which is large or heavy, into or out of the hot cell. In addition, in the case of hot cell equipment which is small and light but has high radioactivity, there is a problem in that a user may be exposed to large amounts of radiation.